Ready indicator for high-voltage switchgear

ABSTRACT

A &#34;ready&#34; indicator for high-voltage switchgear. The switchgear contains switches having normal positions (opened or closed) and switch operators therefor. The switch operators may include stored energy devices which may be charged or uncharged. The switch operators may be selectively coupled to or decoupled from their respective switches. The switchgear may include an automatic control device which, depending upon circuit conditions, causes operation of the switch operators to operate their respective switches to selected positions. Appropriate sensors detect the presence or absence of certain conditions. For example, the sensors may detect the ability or inability of the automatic control device to effect operation of the switch operators, the position of the switch operator or of the switches (open or closed), the charged or uncharged state of the stored energy devices in the switch operators, and whether or not the switch operators are properly coupled to their switches. The sensors provide signals to logic circuitry, which illuminates a light or energizes some other warning device if and only if all of the switch operators, automatic control devices, etc. are in a predetermined desired condition. The light is not illuminated in the event that any conditions of the switchgear are not appropriate or are other than might be assumed. Appropriate indicia may be associated with the light so that if not illuminated, the human operator is led step by step through a check of the switchgear until he ascertains which assumed condition is not present in preventing illumination of the light.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a "ready" indicator for high-voltageswitchgear and more specifically to a "ready" indicator for use with anautomatic control device found in high-voltage switchgear whichindicates the capability of both the control device and the switchgearto perform their intended functions and to give an indication of suchcapability to persons not familiar with the internal workings of eitherthe control device or the switchgear.

2. Brief Discussion of the Prior Art

Numerous control systems and detectors for polyphase electrical systemsand for equipment containing such systems are well-known. One type ofequipment often used or found in polyphase electrical systems ismetal-enclosed switchgear which usually contains a series combinationfor each phase of the system of an interrupter switch and a power fuse.An interrupter switch is an electrical switch which may be manually orautomatically operated (opened or closed) as dictated by therequirements of the system or by requirements of loads connectedthereto. An interrupter switch has the capability of opening the phasein which it is contained and upon such opening interrupting loadcurrents and currents of lesser magnitude flowing in the phase. Suchinterruption normally includes the extinguishment or suppression of ahigh-voltage arc which forms when opening of the phase is attempted. Thearc is extinguished or suppressed in a controlled environment so as tocause little if any distress to the switch itself, to the metal-enclosedswitchgear in which the switch is contained, or to the electrical systemto which this switchgear is connected.

The power fuses serially connected to each interrupter switch areessentially protective devices. Specifically, these power fuses respondto fault currents or other overcurrents flowing in the phase in whichthey are connected and interrupt such fault currents or otherovercurrents upon the occurrence thereof. Interruption effected by thepower fuses involves the extinguishment or suppression of thehigh-voltage arc which is formed incident thereto in a controlledenvironment so as to cause little if any distress to the electricalsystem or to other equipment connected thereto.

Often, it is critical or important that certain loads energized by theelectrical system not be without electrical power for more thanabbreviated times. In this event, two independent electrical sources areoften provided, each source containing appropriate switchgear connectedthereto. Under normal conditions, one of the sources, often termed apreferred source, is connected to the loads through the interrupterswitches in the switchgear connected thereto. The other electricalsource is utilized only if the preferred source is unable to supplyproper electrical power. The other electrical source is therefore oftenreferred to as an alternate source. Connection of the alternate sourceto the load therefore involves the opening of the interrupter switchesin the switchgear connected to the preferred source and the closing ofthe interrupter switches in the alternate source.

Any persons, including utility employees, who are responsible for themaintenance, repair, or operation of switchgear, often do not havedetailed knowledge concerning the internal working of the switchgear.For example, the switchgear connected to the preferred electrical sourceand to the alternate electrical source may be of the type in which theinterrupter switches in the switchgear connected to the preferred sourceare normally closed and the switches in the switchgear connected to thealternate source are normally open. The switches may be operated byautomatic operators, the operator associated with the normally closedinterrupter switches being capable only of automatically opening suchswitches, and the operator associated with the normally open switchesbeing capable of only closing such switches. Should this be the case,return of both sets of switches to their initial condition requiresmanual operation. Moreover, either electrical source may be selected tobe the preferred source, while the other may be selected to be thealternate source. Because of this, the switchgear may permit the removalof each switch operator and appropriate disassociation thereof from itsswitches and interchanging the switch operators in the switchgear.Further the switch operators may involve stored energy sources such assprings which may be in a charged or uncharged condition.

Thus, at any given time it may be important for an operator or otherperson to quickly ascertain the condition, open or closed, or theswitches, whether or not the respective switch operators areappropriately coupled to the switches, whether or not the correct switchoperator is associated with the correct switch (depending upon whichsource is the preferred source and which is the alternate source) andwhether or not the stored energy source in each switch operator isappropriately charged or capable of operating the operator to open orclose the switches associated therewith in the appropriate manner.

There are many other conditions of the switchgear which it is desirablethat a human operator be able to quickly ascertain. As noted above, suchoperators often do not have detailed knowledge of the internal workingsof the switchgear. It goes without saying that they also do not have thedetailed knowledge of the switch operators.

Accordingly, an object of the present invention is the provision of a"ready" indicator for high-voltage switchgear which is convenient andinexpensive and reliable, and from which a human operator may easilyascertain whether or not the condition of the switchgear is appropriatein view of the requirements and conditions of electrical sourcesassociated with the switchgear and of loads connected thereto.

SUMMARY OF THE INVENTION

With the above and other objects in view, the present invention relatesto a ready indicator for high-voltage switchgear. The switchgear is of atype which contains switches having a normal position (opened or closed)and a switch operator therefor. The switch operator may include a storedenergy device which may be in a charged or an uncharged state. Moreover,the switch operator may be selectively coupleable to and decoupleablefrom the switch. The switchgear may also include an automatic controldevice which, depending upon circuit conditions, causes operation of theswitch operator to put the switch in a selected position.

In its broadest perspective therefore, the "ready" indicator of thepresent invention includes appropriate sensors which detect the presenceor absence of certain conditions. For example, the sensors may detectthe ability or inability of the automatic control device to effectoperation of the switch operator, the position of the switch operatorwhich indicates the position of the switch (opened or closed), chargedor uncharged states of the stored energy device in the switch operator,and whether or not the switch operator is properly coupled to theswitch. If there are more than one set of switches and additional switchoperators therefor, the automatic control device may control theoperation of both switch operators and additional sensors may beprovided with such additional switch operators, switches and the likefor determining the appropriate condition thereof. The sensors providesignals to logic circuitry which effects illumination of a light, orenergization of some other warning device, if, and only if, all of theswitches, switch operators, automatic control devices and the like foundin the switchgear, are in an appropriate condition. The light is notilluminated in the event that the condition of the switchgear is notappropriate or is other than it might be assumed to be. Appropriateindicia may be associated with the light so that if an operator observesthat the light is not illuminated, he is led step-by-step through acheck of the switchgear until he ascertains which assumed condition isnot present and preventing illumination of the light.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a "ready" indicator for high-voltageswitchgear according to the principles of the present invention;

FIG. 2 is an electrical schematic diagram depicting in greater detail aportion of the block diagram of FIG. 1.

DETAILED DESCRIPTION

A specific example of a "ready" indicator 10 according to the principlesof the present invention is depicted in FIG. 2. Before a detailedexplanation of FIG. 2 is presented, reference should be had to FIG. 1 sothat the environment of use of the "ready" indicator 10 may be morefully explained and so that the novel function and advantages of the"ready" indicator 10 may be more fully appreciated.

Referring to FIG. 1, there is shown a schematic diagram of a portion ofhigh-voltage switchgear 12 with which the "ready" indicator 10 of thepresent invention is usable. The switchgear 12 includes two inputsections 14 and 16 which are respectively connected to a preferredhigh-voltage source 18 and to an alternate high-voltage source 20. Thepreferred and alternate high-voltage sources 18 and 20 may be derivedfrom the high-voltage system of a utility and may or may not be inphase. Typically, the sources 18 and 20 will be derived from differentportions of the utility system so that in the event one of the sources,say the preferred source 18, fails for any reason, the alternate source20 may be substituted therefore to supply electrical power to aplurality of loads 22 connected to the switchgear 12. The sections 14and 16 may constitute appropriate cables or other conductors connectedto the switchgear 12 by appropriate connections 24 and 26 which may bepotheads, terminators, or the like.

Current flows from the preferred high-voltage source 18 through theswitchgear 12 via a normally closed switch 28 to a bus 30. The bus 30 isconnected to the loads 22 via appropriate taps 32 thereon. The switch 28may be an interrupter switch of any well-known type. Such interrupterswitches 28 have the ability of opening the circuit 18-24-24-30-32 whilethe loads 22 are drawing current from the taps 32. Thus, the switch 28provides the capability of opening the circuit 18-14-24-30-32 under loadconditions and effects the extinguishment of the high-voltage arc thatwill be formed thereupon in a safe manner which causes no distress tothe switchgear 12 or to the utility's electrical system. In series withthe switch 28 may be a high-voltage fuse 34 which protects the circuit18-14-24-30-32 from overcurrents or fault currents in appropriatecircumstances as is well-known.

The alternate source 20 is connectable to the bus 30 via a high-voltagefuse 36 and a normally opened interrupter switch 38 which arerespectively similar to the fuse 34 and the switch 28.

In the normal condition of the switchgear 12, when the preferred source18 experiences no difficulty, the switch 28 is closed, supplyingelectrical power to the loads 22 connected to the taps 32. Should thepreferred source 18 experience difficulty, or an inability to supplysufficient power to the loads 22, the normally closed switch 28 isopened and the normally opened switch 38 is closed.

It is to be understood that the circuit 18-14-24-30-38-26-16-20 depictedin FIG. 1 and constituting a portion of the switchgear 12 is a so-calledone-line diagram thereof. Specifically, as is well known, high-voltagecircuits and switchgear for use therein are generally three phase. FIG.1 does not depict all three phases of such a three-phase circuit,depicting schematically only a single phase thereof. It is to be furtherunderstood that the additional phases of the three-phase switchgear 12may be schematically depicted similar to FIG. 1. Moreover, as iswell-known, the taps 32 may be either three-phase taps or single-phasetaps depending on the character of the loads 22 to which they supplyelectrical power.

The switches 28 and 38 may be respectively operated, that is, opened orclosed, by stored energy switch operators 40 and 42 of the type depictedin commonly assigned U.S. Pat. Nos. 2,954,450 and 3,898,420. The switchoperators 40 and 42 may be of the type in which a stored-energy device,such as a robust spring, is chargable to either open or close the switch28 or 38 to which it is connected, depending upon the initial conditionof such switch. Moreover, the operators 40 and 42 may be of the typewhich may be charged-to-open or charged-to-close a switch such as 28 or38. Further, the switch operators 40 and 42 may be operated eithermanually, as indicated by the input lines 44 and 46, or may be operatedby an automatic or other control device 48 as indicated by the inputlines 50 and 52. That is to say, the stored energy operator or spring ofthe switch operators 40 and 42 may be in its charged-to-open orcharged-to-close condition, either by human manipulation of a handle orthe like (indicated by the input lines 44 and 46) or by the rotation ofa output shaft or other movement of a similar member by a motor (notshown) or other source of motive power contained within the operator 40and 42 and controlled by the control device 48 (as indicated by theinput lines 50 and 52).

The switch operators 40 and 42 are respectively mechanically coupleableto their switches 28 and 38 as indicated by the dashed lines 54 and 56.Preferably, the switch operators 40 and 42 are to the type which may bepartially or completely removed from an appropriate compartment (notshown) in a cabinet or enclosure (not shown) housing the switchgear 12.Such removal of the switch operators 40 and 42, not only effects thedecoupling thereof from the switches 28 and 38, but also permits theoperators 40 and 42 to be adjusted, repaired, maintained or inspected.The switch operators may be interchangeable; the operator 40 may becoupled to the switch 38 and the operator 42 may be coupled to theswitch 28.

In operation, and assuming that the preferred source 18 is appropriatelysupplying electrical power to the loads 22, the switch 28 is closed andthe switch 38 is open. Should the preferred source 18 experiencedifficulty, either a human operator of the control device 48 may operatethe switch operators 40 and 42 to first open the switch 28 and thenclose the switch 38, thus connecting the loads 22 to the alternatesource 20. If and when the preferred source 18 is restored, the switchoperators 40 and 42 may be operated to first open the switch 38 and thenreclose the switch 28 returning the switchgear 12 to its originalcondition.

Utilities and owners of switchgear 12 utilize employees of variouslevels of skill. One shortcoming of present day high-voltage switchgear,generally functionally similar to the switchgear 12 of FIG. 1, is thatoften a detailed understanding of the internal workings thereof isrequired to properly operate, check, test, or otherwise monitoroperation of such switchgear 12. To alleviate this requirement, theready indicator 10 of the present invention is provided.

As more fully explained below, the "ready" indicator 10 includes a logicgate 58 having a plurality of inputs 60 thereto (see FIG. 2). Theseinputs 60 are represented in FIG. 1 by a plurality of boxes which aregiven alphanumeric designations. Also, as more fully explained below,the logic gate 58 and other logical elements associated therewith, mayutilize either so-called negative logic or positive logic. For purposesof the description of the present invention it will be assumed thatpositive logic is utilized, meaning that a "0" is represented by zero ornear zero voltage, while a logical "1" is represented by a positivevoltage. Accordingly, and referring back again to FIG. 1, each input 60to the logic gate 58 represents a point at which a positive voltage or alogical "1" is present if a desirable condition with which each input 60is associated is occurring.

The control device 48 found in the switchgear 12 may be an automaticcontrol device 62 which senses a variety of electrical conditions withinor relating to the switchgear 12. See, for example, commonly assigned,co-filed U.S. Pat. Application Zulaski, Ser. No. 957,267, filed Nov. 3,1978. The automatic control device 62 may be selectively energized by aswitch schematically shown at 64 which applies when closed a positiveoperating voltage 66 thereto on a conductor 68. The positive operatingvoltage 66 may be derived from any convenient source, but is preferablyderived from a source independent of the input sections 14 or 16.Furthermore, when the switch 64 is closed an "automatic mode" of theswitchgear 12 is available; this means that depending upon the conditionof the sources 18 and 20, the automatic control device 62 willappropriately operate the switch operators 40 and 42 as indicated by theinput lines 50 and 52. When the switch 64 is opened, a "manual" mode forthe switchgear 12 is in effect; this means that appropriate operation ofthe switches 28 and 38 must be effected manually as indicated by theinput lines 44 and 46 by a human operator to affect the conditions ofthe switches 28 and 38.

Associated with the switch 64 is an appropriate sensor 70 which isresponsive to the condition of the switch 64. The sensor 70 mayconstitute a microswitch, a photoelectric detector or a directelectrical connection to the conductor 68: In any event, the sensor 70is of a type which applies a positive voltage or a logical "1" to theinput 60 labelled with the letter A when the switch 64 is closed toenergize the automatic control device 62. When the switch 64 is opened,thus de-energizing the automatic control device 62, there is present atthe input 60 labelled A a logical "0".

Appropriately associated with the input section 14 on the source side ofthe fuse 34 may be a sensor 72. See commonly assigned U.S. Pat. No.4,002,976 to Zulaski. One sensor 72 may be provided for each phase ofthe three-phase conductors represented by the input section 14. Thesensors 72 transmit appropriate signals along an input line 74 to theautomatic control device 62. The sensors 72 and the automatic controldevice 62 measure both the magnitude of the time-varying voltages oneach of the conductors 14 as well as measure or detect the phase angletherebetween. In this way, the sensor 72 and the automatic controldevice 62 cooperate to determine if an appropriate three-phaseelectrical signal is incoming from the preferred high-voltage source 18.A sensor 76 is associated with the input section 16 and is similarlyconnected by an input line 78 to the automatic control device 62 to thesame end. Thus, when the automatic control device 62 is called upon toaffect the condition of the switches 28 and 38, part of its decisionmaking process will depend upon the suitability of the sources 18 and 20as determined by the sensors 72 and 76 and the signals present on theinput lines 74 and 78.

The sensors 72 and 76 and the portions of the automatic control device62 to which they are connected by the input lines 74 and 78, may be of atype which are normally energized to perform their judgmental functionwhenever the automatic control device 62 is energized by closure of theswitch 64. If it is desired to defeat the function of the sensors 72 and76 and those portions of the automatic control device 62 to which theyare connected for test or other purposes, there may be provided a groundconductor 80 connected through a normally open switch 82 and from thereto ground 84. The ground conductor 80 may be appropriately connected tothe sensors 72 and 76, the input lines 74 and 78, or appropriateportions of the automatic control device 64. When the switch 82 is open,the sensors 72 and 76 and the automatic control devices 62 are capableof analyzing and making judgments based on the magnitude and the phaseangles of the voltages of the respective sources 18 and 20. If theswitch 82 is closed, the sensors 72 and 76 are grounded, thus preventingthe automatic control device 62 from affecting the condition of theswitches 28 and 38 in response to the condition of the sources 18 and20.

Associated with the switch 82 is a sensor 86 which may be similar to thesensor 70. Regardless of the nature of the sensor 86, it applies to theinput 60, labelled B, a positive voltage or a logical "1" if the switch82 is open; if the switch 82 is closed, the sensor 86 provides at theinput 60, labelled B, a logical "0".

Also associated with the input sections 14 and 16 on the load side ofthe fuses 34 and 36 may be, sensors 88 and 90, respectively. Thesesensors 88 and 90 may be similar to the sensors 72 and 76. The sensors88 and 90 are associated with the input sections 14 and 16 so as totransmit on respective input lines 92 and 94 to the automatic controldevice 62, signals indicative of the voltage magnitude and phaseorientation on the phase conductors of the three-phase input sections 14and 16. The automatic control device 62 leaves switch operators 40 and42 unaltered as long as the magnitude and the phase orientations of thevoltage of the input section 14 remains within predetermined limits.Should the voltage of one or more of the phase conductors of the inputsections 14 fall below the predetermined minimum value, the automaticcontrol device 62 operates the switch operator 40 to open the switch 28and closes the switch 38 by operation of the switch operator 42.

The sensors 88 and 90, as noted above, are sensitive to and cause theautomatic control device 62 to operate the switch operators 40 and 42 inresponse to, among other things, an improper phase relationship betweenthe voltages occurring on the three phases of the sources 18 and 20. Forexample, assuming switch 28 to be closed, and switch 38 to be open, if aphase-to-ground-fault occurs in one phase of the preferred source 18,the fuse 34 in that phase may operate to interrupt current in the phase.Following such fuse operation, with the other two phases of thepreferred source 18 still energized to the bus 30 and the loads 22,there is a danger that so-called single phasing may occur. As iswell-known, single phasing may damage three-phase loads 22. Theautomatic control device 62 now responds to the improper phaserelationship between the voltages in the phases because one of thesensors 88, associated with the faulted and interrupted phase istransmitting on the input line 92 an indication that such phase has beeninterrupted. Accordingly, the automatic control device 62 causes, viainput line 50, operation of the switch operator 40 to open the switch28. Following such opening, the automatic control device 62 causesoperation of the switch operator 42 via the input line 52 to close theswitch 38, thus permitting the loads 22 to draw electrical power fromalternate source 16.

As should be clear, unless the switch 64 is closed and the switch 82 isopen, the automatic control device 62 is unable to effect automatictransfer from the preferred source 18 to the alternate source 20 in theevent that the preferred source 18 is supplying other than the intendedelectrical power to the loads 22. Conveniently, then, it should bepossible to quickly ascertain if the switches 64 and 82 are in theirintended position should later automatic operation of the automaticcontrol device 62 be desired. Such quick inspection is provided by the"ready" indicator 10 of the present invention described in greaterdetail below.

As noted earlier, the switch operators 40 and 42 are respectivelycoupled to their switches 28 and 38 as indicated schematically by thedashed lines 54 and 56; also, the switch operators 50 and 42 areremovable from the cabinet or enclosure (not shown) housing theswitchgear 12. This coupling and uncoupling of the switch operators 40and 42 to and from their respective switches 28 and 38 is indicated byreference numerals 96 and 98. Reference numerals 96 and 98 represent anyof a well-known variety of mechanical couplings which permit selectivecoupling of the switch operators 40 and 42 to their switches 28 and 38.Incorporated into or associated with the couplings 96 and 98, arerespective sensors 100 and 102. The sensors 100 and 102 may bemicroswitches, photoelectric devices, or any other convenient devicewhich provide a positive voltage or a logical "1" on conductors 104 and104, if, and only if, the respective switch operators 40 and 42 areproperly coupled to their switches 28 and 38 through the couplings 96and 98. This positive voltage, or logical "1", is applied to respectiveinputs 60 to the logic gate 58 labelled, respectively, C₁ and C₂. Asshould be obvious, regardless of the condition (opened or closed) of theswitches 28 or 38, proper automatic operation of the switchgear 12 bythe automatic control device 62 requires that both switch operators 40and 42 be coupled to their switches 28 and 38. If either switch operator40 or 42 is not connected to its switch 28 and 38, its associated input60 will have present thereon a logical "0".

As noted earlier, both switch operators 40 and 42 include a storedenergy device such as a spring. The operators 40 and 42 may be in eithera charged-to-open, or a charged-to-close condition. Generally, thesources 18 and 20 will be derived from different portions of theutilities electrical system. Accordingly, the sources 18 and 20 willgenerally not be in phase. As a consequence, if the switch 28 is opened,then the switch 38 must be closed; conversely, if switch 28 is closed,then the switch 38 must be open. This leads to the conclusion that, ifthe switch operator 40 has previously placed its switch 28 in the closedposition, the switch operator 40 is in the charged-to-open condition;also the switch operator 42 must have previously opened its switch 38,and should be in the charged-to-close position. The reverse of thissituation also obtains. Because the normal condition of the switchgear12 is for the switch 28 to be closed, and the switch 38 to be open, theswitch operator 40, should be in a condition indicative of closure ofthe switch 28; the switch operator 42 should be in a position indicativeof the switch 38 being open. As a consequence, sensors 106 and 107 areincorporated into or associated with the switch operators 40 and 42,giving an indication of the condition thereof. If, and only if, theswitch operator 40 is in a condition indicating that the switch 28 isclosed, a logical "1" is provided on a conductor 108 to the input 60labelled D₁. By the same token, if and only if, the switch operator 42is in a condition indicative of the switch 38 being open, does thesensor 106 provide a signal on a conductor 110, which signal is alogical "1". Such signal is applied to the input 60 of the logic gate 58labelled D₂. Conversely, if the switch operator 40 is in a conditionindicative of the switch 28 being open, or if the switch operator 42 isin a condition indicative of the switch 38 being closed, the inputs 60labelled D₁ and D₂ have present thereon a logical "0".

Numerous other inputs 60 may be provided depending on the structure,intended operation and function of the switchgear 12. Some alternativeor additional inputs are described hereinafter.

As previously mentioned, the switch operators 40 and 42 are of the typehaving a stored energy source or spring therein for operation of theswitches 28 and 38. Also as noted previously, the operators 40 and 42may be in either a charged-to-open or a charged-to-close state.Accordingly, the switch operators 40 and 42 may also include or haveassociated therewith, sensors 112 and 114, which may be similar to thesensors 104 and 106. The sensors 112 and 114 detect or otherwise give anindication of the charged or uncharged state of the stored energy memberin the switch operators 40 and 42. Thus, if either of the springs in theswitch operators 40 and 42 are charged, the sensors 112 and 114 provideon respective conductors 116 and 118, positive voltage or logical "1"signals which are respectively fed to inputs 60 labelled E₁ and E₂.Thus, the simultaneous condition of the input 60 labelled D and E foreach operator 40 and 42 yields an indication of the charged-to-open orcharged-to-closed condition of each operator 40 and 42. Specifically, ifa logical "1" is present at both inputs 60 labelled D₁ and E₁, it isknown that the switch 28 is closed and that the switch operator 40 is inthe charged condition. If the input 60 labelled D₁ has a logical "1"present thereat, but the input 60 labelled E₁ has a logical "0" thereat,it is known that the switch 28 is closed, but the operator is notcharged. Similarly, if input 60 labelled D₁ has a logical "0" thereat,and the input 60 labelled E₁ has a logical "1" thereat, it is known thatthe switch operator 40 is charged and that the switch 28 is open. Asimilar analysis of the inputs 60 labelled D₂ and E₂ related to theswitch operator 42 may be made.

It may also be desirable to give a sensible indication of the ability ofthe automatic control device 62 to automatically control the state ofthe switchgear 12. Specifically, even assuming that the switches 64 and82 are in their proper positions, it is possible that the transformedvoltage derived from the sources 18 and 20 used to supply the operatingvoltages 66 to the automatic control device 62 is improper. As notedearlier, this operating voltage 66 may be derived from the sources 18and 20. A signal from the respective sources 18 and 20, proportional tothe voltage thereon, may be provided on respective conductors 120 and122. These signals may be appropriately transformed by transformers 124and 126 to produce the operating voltage 66 for the automatic controldevice 62 on conductors 128 and 130. Both conductors 128 and 130 areconnected to a conductor 132 from which is ultimately derived theoperating voltage 66 for the automatic control device 62 as shown.Appropriate sensors 134 and 136 provide on respective conductors 138 and140 signals indicative of whether the voltage on the conductors 128 and130 is sufficiently high to produce an appropriate operating voltage 66for the automatic control device 62. If, and only if, the operatingvoltage 66 is sufficiently high to properly operate the automaticcontrol device 62 is there provided at respective inputs 60 labelled F₁and F₂ a positive voltage or logical "1". If the voltage 66 is belowthat at which the automatic control device 62 will properly operate,present at the inputs 60 labelled F₁ and F₂ are low or no voltagesignals, or logical "0".

Turning now to FIG. 2, there is described in greater detail, the readyindicator 10 according to the present invention. As previously noted,the ready indicator includes a logic gate 58 which in the specificembodiment depicted is a NAND gate 138. The inputs 60 are fed to theNAND gate 138 as depicted, the alpha-numeric designations labelling eachinput 60 corresponding to the labelled boxes in FIG. 1. Some of theinputs 60 to the NAND gate 138 may be fed directly thereto without anyelectrical or electromechanical transformation thereof. Specifically,although the inputs 60 labelled A, B, F₁ and F₂ in FIG. 1, are shownconnected to the sensors 70,86,134 and 136, respectively, such sensorsneed not be used. More specifically, the input 60 labelled A may beconnected directly to the conductor 68. If, and only if, the switch 64is closed, thereby applying the operating voltage 66 to the automaticcontrol device 62 is a positive voltage or logical "1" present at theinput 60 labelled A. Similarly, the input 60 labelled B may be connecteddirectly to the ground conductor 80. If, and only if, the switch 82 isopen is there a positive voltage or a logical "1" applied to such input;if the switch 82 is closed, the ground conductor 80 is grounded and alow or no voltage or logical "0" is applied to the gate 60 labelled D.Moreover, the conductors 138 and 140 may be connected directly to theconductors 128, 130 respectively. If, and only if, the voltage on suchconductors 128 and 130 is above a certain minimum value is asufficiently high positive voltage or logical "1" applied to the input60 labelled F₁ and F₂.

Other inputs 60 such as those labelled C₁, C₂, D₁, D₂, D₂, E₁ and E₂ inFig. 2 may depend on the open or closed position of a switch or the likegenerally depicted at 140 in FIG. 2, for the application of a logical"1" or a logical "0" thereto. For the present discussion, it will beassumed that the sensors 100, 102, 104, 106, 112 and 114 may include orrepresented by such a switch 140. As noted previously, these sensors andaccordingly the switch 140 may take the form of a microswitch, aphotoelectric detection circuit, a fiber optic detection circuit, or thelike. All that is necessary is that such sensors provide either alogical "1" or a logical "0" depending upon the condition being sensed,and its presence or absence.

Assuming for the time being that all of the inputs 60 to the NAND gate138 are logical "1's", the output of the NAND gage 138 applied to aconductor 142 is a logical "0". This logical "0" is applied to the inputof an invertor or NOT gate 144. The presence of a logical "0" at theinput of the NOT gate 144, produces a logical "1" on the outputconductor 146 thereof. Such logical "1" is applied to the base 148 of anNPN transistor 150 utilized as a simple binary switch. Applied to thecollector 152 of the transistor 150 via a series-connected indicatinglight 154, is a bias voltage 156 which may be the same as or differentfrom the operating voltage 66. Because of the presence of a logical "1"on the base 148 and the bias voltage 156 on the collector 152 of thetransistor 150, the transistor 150 is turned "on", and a path to ground158 is provided for the bias voltage 156 through the indicating light154 via the emitter 160 of the transistor 150. Accordingly, theindicating light 154 is illuminated providing a visual indication thatall of the inputs 60 to the NAND gate 138 are logical "1's". Asdescribed herein, the presence of logical "1's" on all of the inputs 60is indicative of the complete readiness of the automatic control device62. to properly automatically control the condition of the switchgear 12and of the proper condition of the switchgear 12, especially of theswitches 28 and 38. As to the sensors 100,102,104,106,112 and 114 whichmay be properly schematically depicted as represented by the switch 140,FIG. 2 also represents in a schematic fashion a representative way ofderiving logical "1's" on the inputs 60 labelled C₁, C₂, D₁, D₂, E₁, andE₂. Specifically, the bias voltage 156 may be fed through a voltagedivider 162, including a pair of series resistors 164 and 166 to theinput 168 of an invertor or NOT gate 170. A center tap 172 between theresistors 164 and 166 may be connected in series with the switch 140 toground 157. The switch 140 may be a normally open switch. The biasvoltage 156 is of a sufficient positive magnitude to represent a logical"1" considering the effect of the resistors 164 and 166. As long as theswitch 140 remains open, such logical "1" is applied to the input 168 ofthe NOT gate 170. Thus, there appears on the output 174 of the NOT gate170 (the output 174 being the same as the input 60 labelled C₁) alogical "0". As is well-known, if one input to a NAND gate is a logical"0", the output thereof is a logical "1" regardless of the condition ofother inputs thereto. Thus, with a "0" present on the output 174 and onthe input 60 labelled C₁ of the NAND gate 138, there is a "1" on theoutput 142 from the NAND gate 138. This produces a "0" on the outputconductor 146 of the NOT gate 144. Such "0" does not bias the base 148of the transistor 150 sufficiently to permit the transistor 150 to turn"on" and accordingly, indicating light 154 does not become illuminated.The inputs 60, labelled C₂, D₁, D₂, E₁ and E₂ may be connected to outputconductors similar to the output conductor 174 and similarly, connectedto voltage dividers and switches similar to the voltage divider 162 andthe switch 140. If the switch 140 is closed, a "1" is present on theinput C₁. Unless all of the inputs 60 have present thereon a logical"1", the indicating light 154 is not illuminated. There is thus provideda readily ascertainable indication of the proper condition of both theswitchgear 12 and the automatic control device 62 which does not requirea detailed knowledge of internal structure of functioning thereof.

The center tap 172 may also be connected to ground 158 via a seriesvaristor 176. The varistor 176 serves a protective function for thecircuit schematically depicted in FIG. 2 in that should a voltage surgeoccur at the bias voltage 156, the varistor 176 breaks down and conductssuch high level signal to ground protecting the circuitry. Similarly,the input 168 of the NOT gage 170 may be connected to ground 158 via aseries capacitor 178. The capacitor 178 prevents spurious high frequencyharmonics or transients from placing a false "1" on the input 60connected to the NOT gate 170.

Referring again to FIG. 2, there are shown additional optionalfacilities for checking the condition of the indicating light 154.Specifically, it may be desired to provide a way of determining whetherthe indicating light 154 is capable of being illuminated to avoid thefalse impression that switchgear 12 and the automatic control device 62are properly configured or are capable of appropriately controllingelectrical power to the loads 22. More specifically, a push-to-testswitch 180 may be provided which in its normal position completes aseries circuit between the indicating light 154 and the collector 152 ofthe transistor 150. When it is desired to test for the operability ofthe indicating light 154, the push-to-test switch 180, is operated insuch a way as to momentarily connect the indicating light 154 to ground158 through a conductor 182. Release of a push-to-test switch 180reconnects the indicating light 154 to the collector 152. If theindicating light 154 is incapable of illumination, momentary operationof the push-to-test switch 180 will not cause illumination thereof. Onthe other hand, if the indicating light 154 is capable of operating,such momentary operation of the push-to-test switch 180 will causeillumination thereof.

It should be noted that the indicating light 154 may be replaced byother well-known sensible indicators. Specifically, an audible alarm, aflashing vividly colored indicator light, or a relay, may be substitutedfor the indicating light 154 to provide an appropriate indication at anappropriate location of the readiness or not of the switchgear 12 andthe automatic control device 62 to transfer the loads 22 between thesources 18 and 20, depending on the condition of such sources 18 and 20.

The ready indicator 10 of the present invention may include appropriateindicia or instructions 200 near or in the vicinity of the indicatinglight 154. The instructions 200 may instruct all, including the lesssophisticated operator, of appropriate steps to take, depending on thecondition of the indicating light 154. For example, should the operatorassume that the switchgear 12 and the automatic control device 62 are inappropriate conditions to properly supply electrical power to the loads22 depending upon the condition of the sources 18 and 20, but should theindicating light 154 also not be illuminated, instruction number 1 maydirect the operator to first momentarily operate the push-to-test switch180 to determine if the indicating light 154 is illuminable.Instructions may go on to direct that, should momentary operation of thepush-to-test switch 180 inform that the indicating light 154 isilluminable, but is nevertheless not illuminated, the operator may benext instructed to visually ascertain the opened or closed condition ofthe switches 28 and 30. As described above, if the switch 28 is closed,and the switch 38 is opened, there are necessary but not necessarilysufficient conditions present for illumination of the indicating light154. Should the operator ascertain by visual observation that the switch28 is open, and/or the switch 38 is closed, then he knows the reason forthe lack of illumination of the indicating light 154 and that theswitchgear 12 is not in the assumed condition. Should the switch 28 andthe switch 38 be in their assumed respective closed and openedconditions, instruction number 2 may next direct the operator toascertain that the switch operators 40 and 42 are properly coupledthereto via the couplings 96 and 98. This determination may be simply amanual, physical check, that the switch operators 40 and 42 are pushedinto or otherwise properly located in the cabinet or enclosure (notshown) for the switchgear 12. Should the operator determine that theswitch operators 40 and 42 are appropriately coupled to their respectiveswitches 28 and 38, the instruction number 3 may next direct him toascertain that the switch operator 40 is in the charge-to-open conditionand that the operator 42 is in the charge-to-close condition. Should theopertors 40 and 42 be in their appropriate conditions, and should theirstored energy operators also be appropriately charged, instructionnumber 4 may next direct the operator to ascertain by an appropriateelectrical check that the voltage of the sources 18 to 20 areappropriate. It should be noted that various components of theswitchgear 12 could be in other than the assumed condition due to aprevious manual operation of the switch operators 40 and 42 and theirassociated switches 28 and 38, which manual operation is unknown to theoperator who is ascertaining the condition of the indicating light 154.Similarly, previous maintenance, testing or repair of switchgear 12 mayhave placed various components thereof in other than the assumedcondition.

Additional inputs 60 as indicated by the broken-line input 60 to theNAND 138 may also be provided, thus requiring additional conditions bepresent before the indicating light 154 is illuminated. Examples of suchadditional conditions which may be appropritately utilized by the NANDgage 138 via appropriate sensors, are that the sources 18 and 20 aresynchronous, that the frequency of either source 18 or 20 is withintolerance, that the load currents flowing in the bus 30 and the taps 32to the loads 22, are within the interrupting limits of the switches 28and 38 and/or the fuses 34 and 36, that remote switches, fuses,breakers, or relays are in desired predetermined modes, or that anyother condition of the switchgear 12 of the automatic control device 62of the sources 18 or 20, or the loads 22, exists.

The above-described apparatus may take one of at least two differentconfigurations. The first configuration is called "one-way sourcetransfer" in which a loss of the preferred source 18 or reductionthereof to a predetermined level for a predetermined period of timeresults in opening of the switch 28 by the switch opertor 40, followedby closing of the switch 38 by the switch operator 42. Regardless of thecondition of the sources 18 and 20 thereafter, the switch operators 40and 42 may be resettable to their respective charged-to-open andcharged-to-close conditions only by manual operation thereof indicatedby the input lines 44 and 46. Such manual operation not only restoresthe operators 40 and 42 to their appropriate charged condition, but alsoresults in the manual reclosing of the switch 28 and opening of theswitch 38. Of course, as described above, during the time that theswitch 28 is open the switch 38 is closed, the indicating light 154 isnot illuminated, thus alerting the observer to the fact that a sourcetransfer may have taken place. In this configuraion the switch operator40 can be only in the charged-to-open condition, the operator 40 nothaving the capability of being charged-to-close. Similarly, the switchoperator 42 can only be charged-to-close, and may not be in acharge-to-open condition. Nevertheless, if preferred, the switchoperators 40 and 42 which are removable from the cabinet or enclosure(not shown) for the switchgear 12 may be interchangeable. Thisinterchangeability permits either source 18 or 20 to be treated as thepreferred source, while the other source 20 or 18 is is treated as thealternate source. Should this be the case, it must be remembered thatthe switch operator 40, having the capability of being only in thecharge-to-open condition, must be associated with whichever switch 28 or38 is associated with the preferred source while the other switchoperator 42 must be associated with the alternate source. Consequently,the automatic control device 62 may have female plugs (not shown) or thelike, one of which is uniquely associable with the input line 50 or 52connected to the switch operator to the switch operator 40 or 42,associable with the preferred source, and a second female plugassociable only with the input line 50 or 52 connected to the switchoperator 40 or 42, which operates the switch 28 or 38 for the alternatesource. Because the automatic control device must be associated with theappropriate switch operators 40 and 42 in the proper manner, the femaleplug in the automatic control device 62 may have associated therewith,appropriate sensors indicating that the proper input line 50 or 52 isassociated with the proper female plug. These sensors may provideadditional inputs for the NAND gate 138 so that if, and only if, switchoperators 40 and 42 were properly associated with the automatic controldevice 62 is the indicating light 154 illuminated.

In a second configuration of the above described apparatus, referred toas "two-way source transfer," both switch operators 40 and 42 have thecapability of being in either a charged-to-open or a charged-to-closecondition. In this configuration, the switchgear 12 transfers the loads22 from the preferred source 18 to the alternate source 20 if thepreferred source 18 is lost or experiences a significant reduction ofvoltage for a pre-determined period of time. Following such transfer tothe alternate source 20, a retransfer back to the preferred source 18occurs, when such preferred source 18 reassumes its proper state.

As should be obvious to those skilled in the art, additionalconfigurations embodying the principles of the present invention arealso possible. For example, the appratus may assume a "two-way sorucetransfer with bus-tie-switch" configuration in which the bus 30 containsa switch (not shown) similar to the switches 28 and 38 for selectivelypicking up loads 22 connected to appropriate taps 32 on either side ofthe bus-tie siwtch. The proper condition of this switch (open or closed)and of a switch operator (not shown) associated therewith, may provideadditional input for the NAND gate 138 along the lines of the functiondescribed above.

It is to be understood that the above-described embodiments are simplyillustrative of the principles of the present invention. Various othermodifications and changes may be devised, but those skilled in the artwhich will embody the principles of this invention yet fall within thescope and spirit thereof.

I claim:
 1. A ready indicator for switch-gear usable in a high-voltageelectrical system; the switch-gear being of the type having aninterrupter switch in a normal first position, the switch beingselectively movable to a second position by a switch operatorselectively energized by a selectively actuable control deviceresponsive to electrical conditions of the system, the indicatorcomprisingfirst means for generating a first signal if the switch is inthe first position; second means for generating a second signal if theswitch operator is capable of moving the switch to the second position;third means for generating a third signal if the control device iscapable of energizing the switch operator; and first indicating meansfor producing a human-sensible indication of the simultaneous generationof the signals.
 2. A ready indicator as recited in claim 1, furthercomprisingsecond indicating means for indicating the significance of theabsence of the human-sensible indication.
 3. A ready indicator asrecited in claim 2 for switchgear of the type in which the switchoperator is selectively coupleable to the switch and the switch operatorincludes a stored energy source which may be charged or uncharged,wherein the second means comprisesfourth means for generating a fourthsignal if the operator is coupled to the switch.
 4. A ready indicator asrecited in claim 3, wherein the second means further comprisesfifthmeans for generating a fifth signal if the stored energy source ischarged to move the switch to the second position.
 5. A ready indicatoras recited in claim 3, further comprisingmeans for selectivelydetermining the ability of the first indicating means to produce thehuman-sensible indication.
 6. A ready indicator as recited in claim 5,whereinthe second indicating means comprisesindicia which instruct, inthe event of the absence of the human-sensible indication, that thedetermining means is to be first operated followed by inspection of theswitch, the switch operator, the control device and the system in apredetermined order if the first indicating means is capable ofproducing the human-sensible indication.
 7. A ready indicator as recitedin claim 1, whereinthe first switch position is closed and the secondswitch position is open; and the stored energy source is charged to openthe switch.
 8. A ready indicator as recited in claim 1, whereinthe firstswitch position is open and the second switch position is closed, andthe stored energy source is charged to close the switch.
 9. A readyindicator for switch-gear usable with a preferred high-voltageelectrical source and an alternate high-voltage electrical source; theswitch-gear having a normally closed first interrupter switch in serieswith the preferred source and a normally open second interrupter switchin series with the alternate source, the swtiches being selectivelymovable to respective open and closed positions by respective switchoperators selectively energized by a selectively actuable control deviceresponsive to electrical conditions of the sources, the indicatorcomprising:first means for generating a first signal if the first switchis closed; second means for generating a second signal if the secondswitch is open; third means for generating a third signal if the firstswitch operator is capable of opening the first switch; fourth means forgenerating a fourth signal if the second switch operator is capable ofclosing the second switch; fifth means for generating a fifth signal ifthe control device is capable of energizing the switch operators; andfirst indicating means for producing a human-sensible indication of thesimultaneous generation of the signals.
 10. A ready indicator as recitedin claim 9 for switch-gear in which the switch operators are selectivelycoupleable to either switch and include stored energy sources which maybe charged or uncharged, whereinthe third means comprisessixth means forgenerating a sixth signal if the first operator is coupled to the firstswitch; and the fourth means comprisesseventh means for generating aseventh signal if the second operator is coupled to the second switch.11. A ready indicator as recited in claim 10, whereinthe third meansfurther compriseseighth means for generating an eighth signal if thestored energy source in the first operator is charged to open the firstswitch; and the fourth means further comprisesninth means for generatinga ninth signal if the stored energy source in the second operator ischarged to close the second switch.
 12. A ready indicator as recited inclaim 9 for switch-gear in which the switch operators are selectivelycoupleable to either switch and include stored energy sources which maybe charged or uncharged, whereinthe third means comprisessixth means forgenerating a sixth signal if one operator is coupled to one switch, andseventh means for generating a seventh signal if the stored energysource in the one operator is charged to open the one switch; and thefourth means compriseseighth means for generating an eighth signal ifthe other operator is coupled to the other switch, and ninth means forgenerating a ninth signal if the stored energy source in the otheroperator is charged to close the other switch.